In article <jubran-0210961321220001@jubran.csusm.edu>
jubran@mailhost1.csusm.edu "Janet Jubran" writes:>I would question some of your assumptions about the decreasing age of>sexual maturity in modern people.

It has certainly decreased in the last 150 years, due to better nutrition
and health.

> In the Paleolithic period, the lifespan> was barely 20 years of age. Puberty occured prior to age 13, and

It probably occured earlier in hunter-gatherer societies than in
early agricultural societies, because the start of agriculture caused
a decline in human health and nutrition. Does anyone have any data
regarding age of puberty and reproduction in modern hunter gatherer
societies?

>according to Ascent oF Mind, a prolonged childhood is something that has>been increasing over the past few millenia. Also, during the past, the>teens were married by the time puberty set in. This would give them a>societally sanctioned outlet for their sexual impulses which modern teens>do not have. They are told to abstain at a time when sexual drive and>hormones are at their peak.

Not only that, there's a "social adolescence" that often lasts until
their mid-twenties when they become financially independent of their
parents.

>In article <52ogp3$fbu@juliana.sprynet.com>, phis@sprynet.com (James>Howard) wrote:>> My work suggests a cause of this change. The hormone, testosterone, is>> rising rapidly in our society. Increased testosterone increases body size,>> aggression, and sexuality in both sexes. (Testosterone is not "the" male>> hormone, men simply produce more.) People who produce more>> testosterone are more aggressive and sexual, therefore, on average, they>> ultimately make more babies than those who produce less testosterone.>> (People who produce less testosterone can better control their sexual>> activity; over a period of time, they will produce fewer children.)>> Ultimately, the percentage of high testosterone people, of both sexes,>> increases at the expense of low testosterone people. This changes the>> averages of everything affected by testosterone. This is why our kids are>> biggfer, more sexual, and more aggressive than in the past.

There's no doubt that evolution could cause changes to the age of puberty.
But in 100 years? That's far too short a time span for evolution to work.

It's *much* more likely that earlier puberty is caused by better health
and nutrition. In most western countries, middle class kids reach puberty
earlier than working class kids, because their health is better. In the
UK, average age of menarche increased by 1 month during the 1980s,
presumably because govmt policy had caused more kids to live in poverty,
which pulled the average up.

>> The mechanism is simple: higher testosterone boys and girls reach>> sexual maturity faster, increase their numbers faster, and their offspring>> are even earlier and more sexual.

In the UK, this is probably not true. Middle class people reach puberty
earlier, but have kids later, than working class people.

>> Prior to puberty, the brain grows more rapidly than the body; it is a>> competition which the brain wins in infancy and early childhood.>> Because of this brain-body competition, puberty is delayed until the brain>> is almost finished in development. Near puberty, however, testosterone>> increases the body's competitive edge for growth and development which>> continues into adulthood.

The main evolutionary adaptation in Hss is a large brain; I find it very
hard to belive that the development program that nature has given us would
stunt brain growth where there is enough food for the brain to grow
properly. Malnourished children have small brains and many suffer
mental retardation. Well nourished children don't suffer from stunted
brain growth.

>> The advanced frontal lobes of the brain develop last and control formal>> thinking, i.e., higher math, proper language (syntax), and the ability to>> form meaningfully predictive ideas (hypotheses). This is Piaget's final>> stage of human thought development. This stage of brain development is>> directly dependent on final development of the frontal lobes "from about>> age 11 to 14," (Science 1987; 236: 1110). I suggest early puberty>> interferes with this important final development of the frontal lobes. For>> example, it was reported that standardized test scores of 13- and 17->> year-olds of 1986 are lower than those of 1970, whereas the scores of 9->> year-old children have remained relatively equal (Science 1988; 241:>> 1751). I suggest this decline is the effect of puberty, which, in this>> country, on average, is now occurring between age 9 and 13. Our>> children are, on average, losing the ability to handle math and English.

A more likely expalnation is the quality of the school system. Is there
any correllation between age of puberty an brain size, or between
age of puberty and academic achivement?